JP2012205116A - On-vehicle communication device and vehicle-to-vehicle communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for controlling adaptive modulation to resolve communication capability shortage in vehicle-to-vehicle communication.SOLUTION: An on-vehicle communication device: acquires congestion degree information around a vehicle on which the on-vehicle communication device mounted by congestion degree information acquisition means; has communication mode determination information storing correspondence between the congestion degree information and a modulation system or a coding rate; selects the modulation system or coding rate by referring to the acquired congestion degree information and the communication mode determination information; and performs communication by using the selected modulation system or coding rate. Speed of the vehicle on which the on-vehicle communication device mounted, the total number of on-vehicle communication devices of other vehicles around the own vehicle on which the on-vehicle communication device is mounted, location information of the vehicle on which the on-vehicle communication device is mounted, or road traffic information transmitted from outside the vehicle can be utilized as the congestion degree information. Increasing communication speed makes it possible to shorten communication time and reserve a space of a transmission channel, when it is determined that there is congestion around the vehicle.

Description

  The present invention relates to an in-vehicle communication device and a vehicle-to-vehicle communication method, and more particularly to communication management in vehicle-to-vehicle communication.

  Vehicle-to-vehicle communication systems that reduce traffic accidents by providing information to vehicles and drivers and exchanging information between vehicles have been proposed. In an inter-vehicle communication system using an in-vehicle communication device, it is assumed that a low transmission rate is fixedly used in order to ensure high communication quality.

  In vehicle-to-vehicle communication in which unspecified vehicles communicate with each other, the mobile station that is the target of communication changes constantly, so it is not suitable for unicast communication that specifies and communicates with the other party. Is generally adopted.

  In digital wireless communication such as a wireless LAN and a mobile phone, a technique called an adaptive modulation method that adapts the communication speed and output according to the communication environment has been established. Adaptive modulation is premised on communication between a fixed station such as a so-called base station and a mobile station. Information such as signal strength and radio wave quality is exchanged between the fixed station and the mobile station to control the communication speed and communication quality. There is known a method of changing a modulation method or a coding method so that the data can be maintained.

JP 2010-130261 A JP 2010-109610 A JP 2007-281780 A

  When a vehicle using a low transmission speed is crowded in a congested section in an urban area, the transmission path is congested, the communication capacity is insufficient, that is, there is not enough free time for data transmission, May not be able to be sent. In order to avoid this, it is desirable to reduce the occupied time of the transmission path by using an adaptive modulation method in the inter-vehicle communication and changing the communication speed. However, as mentioned above, in vehicle-to-vehicle communication employing broadcast communication, it is difficult to exchange information such as signal strength and radio wave quality on a one-to-one basis. However, the existing method has a problem that the adaptive modulation method cannot be realized.

  The present invention has been made in consideration of the above-described problems, and an object thereof is to provide an in-vehicle communication device capable of performing adaptive modulation control in order to solve a shortage of communication capacity in inter-vehicle communication.

  In order to achieve the above object, the in-vehicle communication device according to the present invention performs inter-vehicle communication by the following means or processing.

As described above, in a situation where the capacity of the transmission path is insufficient, it is considered that many vehicles are crowded. Therefore, when it is determined that there are many vehicles around the host vehicle, a modulation scheme or coding rate that increases the communication speed is set, and the transmission path is assigned to more in-vehicle communication devices. When it is determined that the number of vehicles is small, a modulation scheme or a coding rate that lowers the communication speed is set (hereinafter, a combination of the modulation scheme or the coding rate is referred to as a communication mode). Thereby, since the communication time per vehicle-mounted communication apparatus becomes short, the congestion of a transmission line can be avoided.

  An in-vehicle communication device according to the present invention is an in-vehicle communication device for performing wireless communication with another vehicle, and acquires congestion degree information acquisition means for acquiring congestion degree information around a vehicle on which the in-vehicle communication device is mounted. By referring to the communication mode storage means for recording the communication mode determination information in which the congestion degree information is associated with the modulation scheme or the coding rate, the acquired congestion degree information, and the communication mode determination information. The communication mode selection means for selecting the modulation method or coding rate and the communication means for performing communication using the selected modulation method or coding rate.

  Thus, by acquiring congestion degree information from the outside of the in-vehicle communication device and setting an appropriate communication mode according to the information, the in-vehicle communication device capable of adaptive modulation control, which is an object of the present invention, can be realized. .

  The congestion degree information is a vehicle speed of a vehicle on which the in-vehicle communication device is mounted, and the communication mode determination information is a modulation scheme or code having a higher communication speed when the vehicle speed is low than when the vehicle speed is high. It may be information associated with the conversion rate.

  Thus, when the vehicle speed is high, there are few surrounding vehicles, and when the vehicle speed is low, it can be determined that there are many surrounding vehicles, and there is an advantage that the congestion degree can be determined without acquiring information from outside the vehicle. is there.

  Further, the congestion degree information acquisition means acquires the total number of other in-vehicle communication devices in the vicinity of the vehicle by counting the identifiers of other in-vehicle communication devices in the communication range of the vehicle within a unit time, The communication mode determination information may be information associated with a modulation scheme or coding rate having a higher communication speed when the communication mode determination information is larger than when the total number of other in-vehicle communication devices is small.

  As a result, it is possible to count the total number of other in-vehicle communication devices existing within the communication range of the vehicle, so that it is possible to accurately grasp the degree of congestion around the vehicle as compared with the congestion degree determination from the vehicle speed. There are advantages.

  Further, the congestion degree information is position information of a vehicle on which the in-vehicle communication device is mounted, and the communication mode determination information is more concentrated in traffic than in a case where the vehicle is in an area where traffic is not concentrated. Information associated with a modulation scheme or coding rate having a higher communication speed when the vehicle is in the area may be used.

  Thereby, the traffic volume can be predicted by preliminarily storing the predicted congestion degree for each place in the communication mode storage means and collating with the position information input from the car navigation device or the like. For example, from the acquired position information, if it can be determined that the vehicle is traveling on a main road in the city center, it is determined that the traffic volume is large, and if it can be determined that the vehicle is a general road in the suburbs, it is determined that the traffic volume is low. Such an operation becomes possible.

  In addition, the congestion degree information is road traffic information transmitted from the outside of the vehicle and a traffic situation in the vicinity of the own vehicle derived from the position information of the vehicle on which the in-vehicle communication device is mounted, and the communication mode determination information is The information may be associated with a modulation scheme or coding rate having a higher communication speed when the vicinity of the vehicle is not congested than when the vicinity of the host vehicle is congested.

  Thus, for example, traffic information by VICS (Vehicle Information and Communication System) is received and collated with the position information of the own vehicle acquired by the car navigation device, so that the traffic at the current position It becomes possible to detect the situation accurately.

  The congestion degree information may be a communication mode switching signal transmitted from the outside of the vehicle, and the communication mode determination information may be information in which the communication mode switching signal is associated with a modulation scheme or a coding rate. Good.

  For example, by receiving a signal superimposed on the sound of a traffic information radio or a signal transmitted from a beacon installed beside a road, directing the switching of the direct modulation method without determining the degree of congestion Can be considered.

  Thereby, since the traffic control system etc. can instruct | indicate the switching of a communication mode simultaneously with respect to the vehicle which is drive | working the specific range, compared with the case where each vehicle makes an original judgment, There is an advantage that more efficient transmission line management can be performed.

  The communication mode selection means acquires information from the congestion degree information acquisition means at a set cycle, and when the selected modulation method or coding rate is different from the previous selection condition, the communication method or code The conversion rate may be reset.

  As a result, the in-vehicle device follows the surrounding traffic conditions that change every moment, and communication can always be performed using the optimum communication mode.

  According to the present invention, it is possible to provide an in-vehicle communication device capable of performing adaptive modulation control in order to solve a shortage of communication capacity in inter-vehicle communication.

It is a correlation diagram of communication speed and communication distance. It is a schematic diagram about the communication distance of a vehicle-mounted communication apparatus. It is a figure which shows the function structure of the vehicle-mounted communication apparatus based on 1st Embodiment. It is an operation | movement flowchart of the communication mode selection part based on 1st Embodiment. It is a figure which shows the content of the communication mode determination information based on 1st Embodiment. It is a figure which shows the function structure of the vehicle-mounted communication apparatus based on 2nd Embodiment. It is an operation | movement flowchart of the communication mode selection part based on 2nd Embodiment. It is a figure which shows the content of the communication mode determination information based on 2nd Embodiment. It is a figure which shows the operation | movement outline | summary of the vehicle-mounted communication apparatus based on 2nd Embodiment. It is a figure which shows the function structure of the vehicle-mounted communication apparatus based on 3rd Embodiment. It is an operation | movement flowchart of the communication mode selection part based on 3rd Embodiment. It is a figure which shows the content of the communication mode determination information based on 3rd Embodiment. It is a figure which shows the function structure of the vehicle-mounted communication apparatus based on 4th Embodiment. It is an operation | movement flowchart of the communication mode selection part based on 4th Embodiment. It is a figure which shows the content of the communication mode determination information based on 4th Embodiment.

First, the outline | summary of the vehicle-mounted communication apparatus in this invention is demonstrated, referring FIG. 1 and FIG. In the case of inter-vehicle communication with a fixed communication speed, since the amount of data that can be transmitted per unit time is constant, if the traffic volume increases, the transmission path becomes congested as described above, and the in-vehicle communication device that performs communication using the CSMA method May not be able to send data.

  In order to avoid this, it is necessary to increase the communication speed of the in-vehicle communication device and increase the communication amount per unit time. On the other hand, in digital communication, as shown in FIG. 1, when the communication speed is increased, the communication distance that can maintain a constant communication quality decreases as the communication speed is increased. The trade-off with communication distance must be taken into account. However, vehicle-to-vehicle communication has the purpose of obtaining information around the vehicle and supporting safe driving, so it can communicate with vehicles far away from the vehicle in situations where traffic is concentrated. The need to do is naturally reduced. Therefore, as shown in FIG. 2, it is considered that no problem is caused even if either one is selected.

(First embodiment)
The configuration of the in-vehicle communication device according to the first embodiment will be described with reference to FIG. The in-vehicle communication device 3 includes a vehicle speed acquisition unit 31, a communication mode selection unit 32, a communication mode storage unit 33, a communication mode setting unit 34, and a communication unit 35.

  The vehicle speed acquisition unit 31 is a congestion degree information acquisition unit according to the present invention, and acquires the vehicle speed of the host vehicle from the outside as congestion degree information. As the vehicle speed, it is conceivable to acquire a vehicle speed pulse emitted from a speed detection means possessed by the vehicle, for example, a vehicle speed sensor 36.

  The communication mode selection unit 32 is a communication mode selection unit of the present invention, and refers to the communication mode storage unit 33 based on the vehicle speed acquired by the vehicle speed acquisition unit 31 and selects an appropriate communication mode.

  The communication mode storage unit 33 is a communication mode storage unit of the present invention, and is a communication mode determination information table in which the acquired information is associated with the communication mode to be set. The definition as shown in FIG. 3c is made so that the communication speed decreases as the vehicle speed increases and the communication speed increases as the vehicle speed decreases.

When the communication mode determination information illustrated in FIG. 3C is used, the degree of congestion is 2 when the vehicle speed is from 0 km / h to less than 15 km / h. At the same time, the modulation method corresponding to the degree of congestion 2 is 16 QAM (16 Quadrature Amplitude Modulation) and the coding rate is ½, so the communication speed is 12 Mbps. Further, when the vehicle speed is 15 km / h or higher, the degree of congestion is 1, the modulation method is QPSK (Quadrature Phase Shift Keying), and the coding rate is 3/4. Therefore, the communication speed is 9 Mbps. When the vehicle speed is 40 km / h or more, the degree of congestion is 0, so that the coding rate is ½ and the communication speed is 6 Mbps without changing the modulation method. When the vehicle speed cannot be acquired, the congestion degree is treated as zero.

  The communication mode setting unit 34 has a function of applying the selected communication mode to the communication unit 35 which is a communication unit of the present invention.

  An operation flowchart of the in-vehicle communication device according to the present invention will be described with reference to FIG. The flowchart in FIG. 3B shows a communication mode selection method performed by the communication mode selection unit 32. First, when the operation is started, step S301 for acquiring the vehicle speed of the host vehicle from the vehicle speed acquisition unit 31 is executed.

  Subsequently, the process refers to the communication mode storage unit 33, and transitions to step S302 for selecting a communication mode corresponding to the acquired vehicle speed. At this time, if the vehicle speed cannot be acquired or the corresponding communication mode is not registered, the default communication mode may be selected. Therefore, when step S302 is executed, only one communication mode is selected.

  In step S303, the communication mode acquired last time is compared with the communication mode acquired this time to check whether the contents have changed. If it has changed, the communication mode acquired this time is input to the communication mode setting unit 34, and the process proceeds to S305 which is a timer step. If not, the process proceeds to step S305 without performing anything. Since the communication mode setting unit 34 sets parameters of the communication unit 35 using the input communication mode, a modulation scheme and a coding rate are set for the communication unit by this series of processing.

  In step S305, the process waits until a predetermined time (for example, 10 seconds) elapses, and after that, the process returns to step S301 for acquiring a signal.

  Thus, in this embodiment, the in-vehicle communication device controls the communication speed according to the vehicle speed of the host vehicle. When traveling at high speed, the distance between the vehicles is far away, and it is necessary to communicate with a farther vehicle, so the communication distance has priority over the communication speed, and when traveling at low speed, the vehicle Since the distance between them is considered to be close, the communication speed is given priority over the communication distance. This enables adaptive modulation control in the in-vehicle communication device.

(Second Embodiment)
The configuration of the in-vehicle communication device according to the second embodiment will be described with reference to FIG. 4a. The in-vehicle communication device 4 includes an in-vehicle device signal acquisition unit 41, a communication mode selection unit 42, a communication mode storage unit 43, a communication mode setting unit 44, and a communication unit 45.

  The communication unit 45 receives and collects the identifiers of in-vehicle communication devices of other vehicles within the communication range of the own vehicle within a unit time, and obtains the list as an on-vehicle device signal that is the congestion degree information acquisition unit of the present invention. Input to the unit 41. The on-vehicle device signal acquisition unit 41 counts the total number of input identifiers. This is the number of in-vehicle communication devices in the vicinity of the own vehicle, which is congestion degree information in the present invention.

  The communication mode selection unit 42 is a communication mode selection unit of the present invention, and refers to the communication mode storage unit 43 on the basis of the count result received from the vehicle-mounted device signal acquisition unit 41 and selects an appropriate communication mode.

  The communication mode storage unit 43 is a communication mode storage unit of the present invention, and is a communication mode determination information table in which the acquired number of in-vehicle communication devices is associated with a communication mode to be set. The definition as shown in FIG. 4c is made such that the communication speed increases as the number of in-vehicle communication devices in the vicinity of the host vehicle increases, and the communication speed decreases as the number decreases.

  When the communication mode determination information illustrated in FIG. 4C is used, when the number of in-vehicle communication devices in the communication range is less than 50, the congestion degree is 0, the modulation method is QPSK, and the coding rate is 1 / Therefore, the communication speed is 6 Mbps. When the number exceeds 50, the degree of congestion is 1, so that the modulation rate remains the same, the coding rate is 3/4, and the communication speed is 9 Mbps. When the number exceeds 100, the degree of congestion is 2, the modulation method is 16QAM, and the coding rate is ½, so the communication speed is 12 Mbps.

  The communication mode setting unit 44 has a function of applying the selected communication mode to the communication unit 45 that is a communication unit of the present invention.

An operation flowchart of the in-vehicle communication device according to the present invention will be described with reference to FIG. The flowchart in FIG. 4B shows a communication mode selection method performed by the communication mode selection unit 42. First, when the operation is started, step S401 for acquiring the total number of in-vehicle communication devices counted by the in-vehicle device signal acquisition unit 41 is executed. The subsequent processing is the same as the operation flowchart 3b according to the first embodiment.

  In the present embodiment, as shown in FIG. 5, the communication speed is controlled by the number of other in-vehicle communication devices in the vicinity of the host vehicle. When the number of other in-vehicle communication devices is small, the transmission speed is lowered because congestion of the transmission path does not occur, and when the number is large, the communication speed is increased to secure a free transmission path. In the case of this embodiment, compared with the first embodiment, there is an advantage that it is possible to accurately know how much space is available on the transmission path around the own vehicle. For example, when the communication time of an in-vehicle communication device that performs communication at regular intervals is 10 ms and there are 50 in-vehicle communication devices in the communication range, it can be seen that the usage rate of the transmission path is about 50%.

(Third embodiment)
The configuration of the in-vehicle communication device according to the third embodiment will be described with reference to FIG. 6a. The in-vehicle communication device 6 includes a current position acquisition unit 61, a communication mode selection unit 62, a communication mode storage unit 63, a communication mode setting unit 64, and a communication unit 65.

The current position acquisition unit 61 is a congestion degree information acquisition unit of the present invention, and acquires information related to the current position of the vehicle from the outside. Specifically, the navigation device 71 acquires the position information of the own vehicle and inputs it to the current position acquisition unit 61. The acquired information may be, for example, a numerical value or a character string of address data in units of municipalities, or a numerical value of the zip code at the current position. Alternatively, it may be a road number (eg: National Route 20), a road name (eg: Meiji-dori), or a section name (eg: Kandabashi-Edobashi).
This is the congestion degree information in the present invention.

  The communication mode selection unit 62 is a communication mode selection unit of the present invention, and selects an appropriate communication mode with reference to the communication mode storage unit 63 based on the acquired position information.

  The communication mode storage unit 63 is a communication mode storage unit of the present invention, and is a communication mode determination information table in which the acquired current position is associated with the communication mode to be set. The definition as shown in FIG. 6c is made so that a higher communication speed is obtained for an area with a high traffic volume, and a lower communication speed is provided for an area with a small traffic volume.

  When the communication mode determination information illustrated in FIG. 6C is used, if the current position is Shinjuku-ku, Tokyo, the degree of congestion is 3, the modulation method is 16QAM, and the coding rate is 3/4. Is 18 Mbps. In the case of Akiruno City in Tokyo, the degree of congestion is 0, so the modulation method is BPSK, the coding rate is ½, and the communication speed is 3 Mbps.

  The communication mode setting unit 64 has a function of applying the selected communication mode to the communication unit 65 that is a communication unit of the present invention.

  An operation flowchart of the in-vehicle communication device according to the present invention will be described with reference to FIG. The flowchart in FIG. 6B shows a communication mode selection method performed by the communication mode selection unit 62. First, when the operation is started, the current position acquisition unit 61 executes step S601 for acquiring the current position. The subsequent processing is the same as the operation flowchart 3b according to the first embodiment.

  As described above, in the present embodiment, the communication speed is controlled after determining whether the vehicle is in an urban area, a suburb, a general road, or a highway in conjunction with the car navigation device. . By registering in advance in the communication mode storage unit 63 an area where the capacity of the transmission line is chronically insufficient, there is an advantage that resource control of the transmission line in accordance with the actual situation is possible.

  In the case of this embodiment, for example, when the current position is “Shinjuku-ku, Tokyo” and “Meiji-dori”, a plurality of elements may be combined.

(Fourth embodiment)
The configuration of the in-vehicle communication device according to the fourth embodiment will be described with reference to FIG. 7a. The in-vehicle communication device 8 includes a current position acquisition unit 81a and a traffic information acquisition unit 81b, a communication mode selection unit 82, a communication mode storage unit 83, a communication mode setting unit 84, and a communication unit 85.

  In the present embodiment, the current position acquisition unit 81a and the traffic information acquisition unit 81b correspond to the congestion degree information acquisition unit. The current position acquisition unit 81a is connected to the navigation device 71 and acquires position information of the own vehicle. Moreover, the traffic information acquisition part 81b receives road traffic information via a communication medium from the vehicle-mounted communication apparatus exterior. The communication medium may be a radio signal used for road-to-vehicle communication, or a signal superimposed on the sound of roadside radio. Further, VICS (registered trademark) information received by the car navigation device may be used. In this embodiment, the traffic information acquired via the roadside device (beacon) 91 will be described as an example. The position information of the own vehicle and the traffic information received from the roadside device are the congestion degree information in the present invention.

  The communication mode selection unit 82 is a communication mode selection unit according to the present invention. The communication mode selection unit 82 refers to the communication mode storage unit 83 after acquiring the traffic situation at the current position based on the acquired position information and traffic information, and appropriately Select the appropriate communication mode. In the present embodiment, the traffic information is classified into a congestion type (smooth / traffic concentration / congestion) and a road type (general / high speed). For example, if “Current location: Metropolitan Expressway No. 4 descent” and the acquired traffic information includes “Metropolitan Expressway No.4 descent: Traffic jam”, it is determined that “Current location traffic situation: Traffic jam”. Then, determine the communication mode.

  The communication mode storage unit 83 is a communication mode storage unit of the present invention, and is a communication mode determination information table in which the traffic situation at the current position is associated with the communication mode to be set. The definition as shown in FIG. 7c is made so that the communication speed is higher in the congested case than in the non-congested case.

  When the communication mode determination information illustrated in FIG. 7c is used, if the acquired traffic information is “Metropolitan Expressway Route 4: Traffic Concentration” and the acquired current position is Metropolitan Expressway Route 4, Is determined as “concentration of traffic on the highway”, the congestion level is 0, the modulation method is QPSK, and the coding rate is ½, so the communication speed is 6 Mbps. When the acquired traffic information is “National highway No. 20: traffic jam” and the acquired current position is the national highway No. 20, it is judged as “congestion on general road”, so the degree of congestion is 2, and the modulation method Is 16QAM and the coding rate is ½, so the communication speed is 12 Mbps. When the current position is an expressway and traffic is smooth, the degree of congestion is −1. Therefore, the modulation method is BPSK, the coding rate is 3/4, and the communication speed is 4.5 Mbps. When there is a traffic jam on the highway, the degree of congestion is 2, the modulation method is 16QAM, and the coding rate is 1/2, so the communication speed is 12 Mbps.

  The communication mode setting unit 84 has a function of applying the selected communication mode to the communication unit 85 that is a communication unit of the present invention.

An operation flowchart of the in-vehicle communication device according to the present invention will be described with reference to FIG. The flowchart in FIG. 7B shows a communication mode selection method performed by the communication mode selection unit 82. First, when the operation is started, step S801 for acquiring the current position is executed from the current position acquisition unit 81a. Next, step S802 for acquiring traffic information around the host vehicle is executed from the traffic information acquisition unit 81b. The subsequent processing is the same as the operation flowchart 3b according to the first embodiment.

  As described above, in the present embodiment, information on the degree of congestion around the host vehicle is received from the outside of the in-vehicle communication apparatus, and the communication speed is controlled after determining the communication mode. By receiving information about the degree of congestion from the outside, there is an advantage that accurate transmission path resource control according to the situation is possible.

  The traffic information acquisition unit 81b may acquire a signal that directly indicates the modulation method from the roadside device or the like instead of the traffic information. In this case, the communication mode selection unit 82 refers to the communication mode storage unit 83 and selects the communication mode corresponding to the received signal regardless of the state of the current position acquisition unit 81a. For example, when the communication mode determination information is as shown in FIG. 7c and the traffic information acquisition unit 81b receives a signal “congestion level: 2” from the roadside device, the communication mode selection unit 82 sets the corresponding modulation method as “16QAM” is selected as “1/2” as the corresponding coding rate.

  The above description is merely an example for explaining the present invention, and the present invention should not be construed as being limited to the above embodiment. For example, in the present embodiment, a plurality of conditions are set for the communication mode storage units 33, 43, 63, and 83, but only “normal (low speed communication)” and “specific conditions (high speed communication)”. It is good. In addition, a communication medium that is not illustrated can be used, or a combination of a plurality of information such as “vehicle speed” and “the number of in-vehicle communication devices in the vicinity of the vehicle” can be considered for determining the degree of congestion. Further, the present invention may be realized by software having the illustrated configuration. In the above description, information such as the vehicle speed and the number of in-vehicle communication devices is once converted into a numerical value indicating the degree of congestion. However, the information may correspond to the direct communication mode.

3, 4, 6, 8 Vehicle-mounted communication device 31 Vehicle speed acquisition unit 41 Vehicle-mounted device signal acquisition unit 61, 81a Current position acquisition unit 81b Traffic information acquisition unit 32, 42, 62, 82 Communication mode selection unit 33, 43, 63, 83 Communication mode storage unit 34, 44, 64, 84 Communication mode setting unit 35, 45, 65, 85 Communication unit 36 Vehicle speed sensor 71 Navigation device 91 Roadside (beacon) device

Claims (14)

An in-vehicle communication device for performing wireless communication with other vehicles,
Congestion level information acquisition means for acquiring congestion level information around the vehicle on which the in-vehicle communication device is mounted;
A communication mode storage unit that records communication mode determination information in which the congestion degree information is associated with a modulation scheme or a coding rate;
A communication mode selection means for selecting a modulation scheme or a coding rate by referring to the acquired congestion level information and the communication mode determination information;
And a communication means for performing communication using the selected modulation scheme or coding rate. The congestion degree information is a vehicle speed of a vehicle on which an in-vehicle communication device is mounted,
The in-vehicle communication device according to claim 1, wherein the communication mode determination information is associated with a modulation scheme or a coding rate that has a higher communication speed when the vehicle speed is low than when the vehicle speed is high. . The congestion degree information is the total number of other in-vehicle communication devices around the vehicle where the in-vehicle communication device is mounted,
The congestion degree information acquisition means acquires the total number of other in-vehicle communication devices around the own vehicle by counting the identifiers of other in-vehicle communication devices in the communication range of the own vehicle within a unit time.
The communication mode determination information is associated with a modulation scheme or a coding rate having a higher communication speed when the total number of the other in-vehicle communication devices is large than when the number is small. The in-vehicle communication device described in 1. The congestion degree information is position information of a vehicle on which an in-vehicle communication device is mounted,
The communication mode determination information corresponds to a modulation method or coding rate having a higher communication speed when the vehicle is in an area where traffic is concentrated compared to the case where the vehicle is in an area where traffic is not concentrated. The in-vehicle communication device according to claim 1, wherein the in-vehicle communication device is attached. The congestion degree information is road traffic information transmitted from the outside of the vehicle, and traffic conditions in the vicinity of the own vehicle derived from the position information of the vehicle on which the in-vehicle communication device is mounted,
The communication mode determination information is associated with a modulation scheme or a coding rate that has a higher communication speed when the vicinity of the vehicle is not congested than when it is congested. The in-vehicle communication device according to claim 1. The congestion degree information is a communication mode switching signal transmitted from the outside of the vehicle,
The in-vehicle communication device according to claim 1, wherein the communication mode determination information is associated with the communication mode switching signal and a modulation method or a coding rate. The communication mode selection means acquires information from the congestion degree information acquisition means at a set period, and when the selected modulation scheme or coding rate is different from the previous selection condition, the modulation scheme or coding rate The in-vehicle communication device according to any one of claims 1 to 6, wherein the in-vehicle communication device is reset. One in-vehicle communication device is a vehicle-to-vehicle communication method for performing wireless communication with another vehicle,
Obtain congestion information around your vehicle,
Based on the communication mode determination information in which the correspondence between the acquired congestion degree information and the modulation method or coding rate is recorded, the modulation method or coding rate is selected,
A vehicle-to-vehicle communication method comprising performing communication using a selected modulation method or coding rate. The acquired congestion information is the vehicle speed of the vehicle on which the in-vehicle communication device is mounted,
The inter-vehicle communication method according to claim 8, wherein when the vehicle speed is low, a modulation scheme or a coding rate that selects a higher communication speed than when the vehicle speed is high is selected. The acquired congestion degree information is the total number of other in-vehicle communication devices in the vicinity of the vehicle on which the in-vehicle communication device is mounted,
The inter-vehicle communication method according to claim 8, wherein when the total number of the other in-vehicle communication devices is large, a modulation method or a coding rate having a communication speed higher than that when the number is small is selected. The acquired congestion degree information is position information of a vehicle on which the in-vehicle communication device is mounted,
9. The modulation method or the coding rate is selected, which has a higher communication speed when the vehicle is in an area where traffic is concentrated than when the vehicle is in an area where traffic is not concentrated. Vehicle-to-vehicle communication method described in 1. The acquired congestion degree information is road traffic information transmitted from the outside of the vehicle, and traffic conditions in the vicinity of the host vehicle derived from the position information of the vehicle on which the in-vehicle communication device is mounted,
The vehicle-to-vehicle communication method according to claim 8, wherein a modulation method or a coding rate having a higher communication speed is selected when the vicinity of the host vehicle is not congested. The acquired congestion information is a communication mode switching signal that is transmitted from the outside of the vehicle and specifies a modulation method or a coding rate,
The vehicle-to-vehicle communication method according to claim 8, wherein a designated modulation method or coding rate is selected. 9. The congestion degree information around the vehicle is input at a set cycle, and the communication mode is reset when the selected modulation method and coding rate differ from the previous selection conditions. The vehicle-to-vehicle communication method according to any one of 13.

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